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???
12/16/05 13:39
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#105357 - dont do it
Responding to: ???'s previous message
I need to connect 7805 to a 35VDC rectified o/p.
For this I need to produce a voltage drop of 20 V before giving it to 7805.
can any one suggest me suitable means to do it.

dont do it, 35V is on the edge of what the 7805 can tolerate and the drop resistor is a waste. Use a small switcher such as the PT6302 it can tolerate a larger Vin and need no drop resistor. (I have used more than 10.000 PT6302s and not lost one)

Erik

http://focus.ti.com/docs/prod...t6302.html

List of 33 messages in thread
TopicAuthorDate
Add on card programming            01/01/70 00:00      
   please clarify            01/01/70 00:00      
      RE: please clarify            01/01/70 00:00      
         (E)ISA addressing            01/01/70 00:00      
            IOW and IOR            01/01/70 00:00      
               not explicitly            01/01/70 00:00      
                  IRQ in EISA slot            01/01/70 00:00      
                     interrupt            01/01/70 00:00      
                        QBASIC programming            01/01/70 00:00      
                           reply            01/01/70 00:00      
                              DIP Switch Address Setting in EISA card            01/01/70 00:00      
                                 DIP switches...            01/01/70 00:00      
                                    card design enclosed            01/01/70 00:00      
                                       comparator            01/01/70 00:00      
                           QBASIC live and well.            01/01/70 00:00      
                              NT - not quite            01/01/70 00:00      
                                 timing in Win?            01/01/70 00:00      
                              QBasic Lives!!!            01/01/70 00:00      
   refer to 'Barry B Brey'            01/01/70 00:00      
   EISA Bus interfacing            01/01/70 00:00      
      beware if (E)ISA bus books            01/01/70 00:00      
   Try this?            01/01/70 00:00      
      Power resistor selection            01/01/70 00:00      
         dont do it            01/01/70 00:00      
            LM317 is an option            01/01/70 00:00      
               Wasteful!            01/01/70 00:00      
                  if op can...........            01/01/70 00:00      
                     Power!            01/01/70 00:00      
         basic Ohm's law            01/01/70 00:00      
            Trouble shoot            01/01/70 00:00      
               heating            01/01/70 00:00      
                  Reply : Heating            01/01/70 00:00      
                     if you refer to D4 then            01/01/70 00:00      

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